Hypothermia puts surgical patients at risk for adverse outcomes. Traditional passive warming methods are mostly ineffective in reducing hypothermia. New-technology passive warming holds promise as an effective method for promoting and sustaining normothermia throughout surgery. The purpose of this retrospective cohort study was to compare the effectiveness of new-technology passive warming with traditional methods. We measured core body temperature at anesthesia induction and at the end of surgery for patients undergoing robotic-assisted prostatectomy/hysterectomy in the lithotomy position who received either new-technology passive warming (n ¼ 30) or traditional linens and gel pads (n ¼ 35). The traditionally warmed cohort had no change in temperature (35.9 C AE 0.6 C presurgery vs 35.9 C AE 0.7 C postsurgery; t ¼ 0.47; P ¼ .66). The intervention cohort showed a significant increase in temperature (35.75 C AE 0.52 C presurgery vs 36.30 C AE 0.53 C postsurgery; t ¼ 4.64; P < .001). A repeated-measure analysis of variance adjusting for surgery duration and fluid administration confirmed the significance (F ¼ 17.254; P < .001), suggesting that new-technology passive warming may effectively complement active warming to reduce perioperative hypothermia. AORN J 102 (August 2015) 183.e1-183.e8. ª AORN, Inc, 2015. http://dx